I’m currently building an extension at the rear of my house, I would like the tv cables run into the extension before the internal walls and ceiling are fitted, for a 3rd box, rather than run external cables and drilling through fresh walls and plasterwork.
Unfortunately I have only been able to contact offshore call handlers who don’t seem to understand what I require.
As you have the builders onsite you could get them to do the wall drilling and install trunking for the coaxial and Ethernet cables, have a draw rope for the coaxial cable if necessary. It's best to terminate the Ethernet cable at an RJ45 wall plate. You'll then need one visit from a VM technician to pull through the cable to get the installation done.